Checklist to Troubleshoot a Faulty Embedded System in Your PCB

Kids these days are much smarter than we were. When I was six, all I cared about was watching Sesame Street every evening. My son, on the other hand, regularly searches for his favorite cartoons on Youtube and asks for the correct phrases to type in to receive the exact results he’s looking for. Even at such a young age, he understands that asking smart questions leads to quicker, and more efficient, solutions.

Although finding the right terms to type into Youtube may not be your first priority as an engineer, you still need to practice asking smart questions. For instance, if you’re dealing with a damaged embedded system PCB, asking timely questions could save you significant time and money down the road and prevent you from causing further damage.

How to Avoid Further Damaging Your Faulty PCB

Designing embedded systems can be pretty fun, especially for applications that challenge you to utilize the best of your skills. However, when hardware breaks down unexpectedly, you may find your testing lab filled with damaged PCB components.

When I was a young engineer, I was very proud of my designs and would often get defensive when any of my hardware was sent back due to failure. Once, while hastily trying to prove that external factors had caused the problems I was blamed for, I powered up my PCB without considering the consequences. I learned a valuable lesson that day, as an electrical spark led to the track breaking into multiple parts.

Never power up a damaged PCB immediately, regardless of the severity of the reported symptoms. For instance, if you’re dealing with what seems like a simple blown fuse, investigate the root cause of the blown fuse instead of simply replacing it and powering up the PCB. When it comes to PCB design, what you can visually observe is normally just the tip of the iceberg.

Be Smart and Ask These Questions

Being hastytroubleshooting a faulty embedded system PCB can result in irreparable damages. A simple replacement of shorted communication integrated circuit (IC) may result in catastrophic damages that require you to completely replace the PCB. To help prevent that scenario, ask these questions whenever you are working with a faulty PCB:

1. Are any components or Integrated Circuits (IC) broken?

A serious surge of lightning normally results in cracked or burnt components. Carefully perform a visual check on all of the components for any signs of damage. Pay extra attention to components that are in direct exposure to external connections. Power supply, communications, and inputs, for instance, are the usual suspects for an incoming surge.

Obvious tell-tale signs of damages.

2. Is there an acrid burnt smell on the PCB?

I bet you’ve burnt some ICs in your life to know what the burnt smell of semiconductors is like. Well, it’s time to put your smelling expertise to use and take a few whiffs of different areas of the PCB. Sometimes, even when there are no visible traces of burnt components, the burnt smell lingers long after the PCB is removed from sight.

3. Do you immediately spot broken tracks?

When a short circuit on a load or components causes excessive current on copper tracks, it can result in a break. Look for clean breaks or messy copper track damage with parts of the PCB blackened. Tracing the broken track typically points you to the main culprit of the faulty PCB. Fixing broken tracks usually involves manual soldering of thin wires and requires high precision.

4. Is the positive supply shorted to ground?

Sometimes, you might have a dysfunctional PCB with no visual indications or odors that hint of damages. Before you power up your PCB, however, grab your trusted multimeter and perform a quick check on all positive supply connections to ensure that they’re not shorted to ground. If your embedded system works on +3.3V, be sure to check all voltages that exist on the PCB.

Short circuits usually leave obvious signs.

Powering Up the Faulty PCB

Following the step-by-step guide above usually helps you identify damaged components on a PCB. However, there are cases where the faults are more subtle and require powering up the PCB for further diagnosis.

A great way to power up your PCB while minimizing the risk of damages is to probe the microcontroller power supply with the multimeter as you turn on the power. If it doesn’t rise to the expected level, quickly turn off the power supply and use your own hands to check for overheated components.

If a component is badly damaged, a few seconds of current flowing through is more than enough to create excessive heat. To minimize chances of damage, you may consider tracing individual connections using PCB design software like Altium Designer.